Shears with teeth for cutting along zigzag lines



Aug. 26, 1952 s, sH 2,607,986

SHEARS WITH TEETH FOR CUTTING ALONG ZIGZAG LINES Filed Aug. 19, 1947 INVENTOR ava Yfierr.

ATTORNEY Patented Aug. 26, 1952 SHEARS WITH TEETH FOR CUTTING ALONG ZIGZAG LINES Sava I. Sherr,-New York, N. Y., assignor to Samuel Briskman, New York, N. Y.

, Application Augusiis, 1947, Sejrial No. 769,355

2 Claims.

This invention is an improvement in hand scissors or shears with teeth for severing cloth along zigzag lines to make a serrated instead of astraight edge. i T

The invention comprises a novel form of such shears that can be produced in a shorter time and with less work and labor anda smaller number of processing steps than have previously been required; and an important object of the invention'is to provide shears of this kind of superior design at considerably reduced cost. 7

Previously in the manufacture of hand shears of this type, several metal strips or blanks were bunched together with their wide flat'sides in contact and tilted in coinciding positions, and secured in operative relation to a rotary cylinder having sharp cutter projections on its circumfere'nce. The cylinder was revolved to carry the way of example only, and in practice various projections or cutter members, which hadtriangularpointed extremities. with sharp inclined edges against one of the superposed edges of each blank and straight through the bunched blanks to form the teeth. The blades were fed sidewise toward the cylinder till the cutting was completed. These teeth thus had a triangular shape and. their lateral faces were tilted at an angle to theopposite wide-parallel faces or sides of theblade; also each tooth'had lateralfaces convergin to a point or edge.extending from one of the'wide opposite faces of the blade to the other, and all projecting along. one edge of the blade. Because the teeth were cut at. an angle, the edges of each were sharper along one side or wide face of the blade than along the other,

the sharper edges being the leadingedges when the shears were finished. The blades then had to be sheared to some extent; that is. each tooth was cut or shaved away, so as to form a small strip of surface, along said acute, leading edges thatmade a slight angle with the remainder offthe lateral faces of the tooth. .The blades were then 'Iapped to impart to them, and especially to the narrow. sheared surfaces, the proper finish to ensure smooth cutting by saidteeth changes in structural details and mode of opera tion can be adopted 1 without deviation from the essential designandstructure wherein the inven' tion resides.

'On the drawings, Figure '1 is a'view partly in section showing-the operation of cutting teeth for shears according to my invention. i Figure2 a front elevation of part of the mechanism shown inFigure 1.

Figure 3 is a section on line 3-3 of Figure {I shows how the step of lapping and polishing is performed.

Figures 5 and 6 are diagrammatic views ill-S80 tion' showing the result of the, lapping process; the toothed blades locking as if in section along a line acrossthe lower half-of Figure 4, viewed from 'abiove. v

Figure 7 shows in part a pai -0f finished shears embodying this invention and Figures'8, 9 and 10 are diagrammatic views showin details of the toothed blades for my proved shears.

The numeral 1 indicates a rotary disk or head adapted to be operated by a shaft 2 suitably supported .in. one or more bearings 3. This disk carries several strips. or fiat bars of metal .or blanks 4, held in such position that they'can be revolved past the triangular ends of a row of 1 cuttersi, which. are mounted on a support 6 and canbe set close enough. to. the blanks to en gage theedges thereof projecting out from the faceof the disk I to form teeth, with lateral faces 1 and flintersecting in projectin -edgesfi. The

- disk and cutters ,5 move relatively closer'when the machine is in operation. The disk I has slots Hi, in which the blanks 4 are made fast by looking bars H, secured by screws I2. The slots are not radial, but so placed that if the centerline were extended, it would pass to one side of the axial center of the shaft 2, as indicated in Fig- F ure 1,.

ure 2. The blades are thus offset from the axis of the shaft 2, for cutting, to the same extent as they are offset from the pivot joining the two halves or jaws of the finished shears when the blades are attached to said halves in their final positions. See Figure 7. Also the slots ID are inclined somewhat to the front face of the disk, so that the triangular teeth are cut at a small angle to the wide opposite faces or fiat sides of the blade, and the lateral faces "I and 8 and the front edges 9 of the teeth are therefore inclined to said sides for say about ten degrees. The faces 1 and 8 will not be flat but are small elements of conical surfaces described with reference to the center of the shaft 2 as a common axis by the diagonal sides of the pointed ends of the cutters 5. A machine of such construction as to I produce triangular teeth out this way into the blades 4 is shown and described in my prior ap plication, Serial No. 681,257, filed July 3, 1946 now Patent Number 2,537,164 issued January 9, 1951; and its structural characteristics are set forth in the claims of said application: The cutters 5 are made .fast onthe support Bby a band 3 and screws M, or other suitable means. The head I and support 6 approach slowly during operation, either or both being movable for this purpose.

To finish the teeth the blades 4 are worked in pairs as illustrated in Figure 4. 'The apparatus employed in this step comprises a fixed standard or post |5 having a vertical recess or slot 5 for one of the toothed blades 4; and a swinging arm I8 with a similar recess for another toothed blade 4. The blades are secured to the standard and 7 the arm by screws or other fastening means. The arm I8 is oscillated by a shaft l9; mounted in a bearing at the top of the post [5. The lapping is accomplished by operating the arm I8 to swing the toothed blade it carries from side to side past and in rubbing orgrindingcontact with the toothed blade onfthe standard IS. The teeth on these two blades, which are of equal length, are so located that the teeth on one enter the recesses between the teeth on the other.

Thus the lateral faces 1 and 8 of the teethare carried repeatedly into and out of frictional engagement. The blades are mounted in the post I5 and arm I8 as shown in Figures 5 and 6, and the lateral faces of theteethrub against one another adjacent the more acute or. advanced edges thereof. These edges are made acute because of the inclination of the teeth to the flatfopposite sides. of the blades, makin them sharper along one fiat side of the blade than the other. As a result the blades wear away these lateral faces a bitalong the advanced or acute leading edges and produce a narrow strip of surface indicated at 2|, which extends across the lateral faces! and 8 from one end of the blade to the other at the acute or leading edges thereof. The. surface of thi strip makes a minute angle with the remainder of the lateral surfaces 1 and.8. When the blades are mounted in a pair of shears as indicated in Figure '7, the two blades present their effect the' cutting of a piece of cloth or other material which is to be severed or trimmed. The blades in question can be attached in any suitable manner to the two halves 22 indicated in part in Figure 7, these halves or jaws being joined together by a pivot 23 secured by a nut or cap 24, the handles being at the other endsfnot shown in the drawings, to make the shears complete.

In practice, as "setfo'rth in my application,

Serial No. 5,444, filed January 30, 1948, for patent on the apparatus and process for lapping toothed blades, the shaft I9, as it is rocked to swing the arm l8 from side to side with the two blades 4 in close proximity so that the faces 1 and 8 of the teeth on both come into rubbing contact, is also actuated so that this arm slides alon the shaft .-|9 as the wearing away of the strip 2| proceeds. This axial feeding is stopped when the wearing away of the strip 2| is completed; but

the swinging movement of the arm can continue form these strips 2| on each of the lateral faces l and 8 of the teeth on the two blades in such manner as to make them elements of conical surfaces, which have the center of the shaftv |9 as a common axis. The strips 2| would therefore assume such shape, even if the faces I and 8of the teeth were not previously cut so as. to be small elements of concentric conical surfaces. By forming the teeth as above described in connection with the operation of the apparatus shown in Figures 1, 2 and 3; and by making the faces 1 and 8 conical in the first place before the lapping is done, the lapping is rendered much easier and more effectiveand can be completed in a much shorter time. This mode of operation is very advantageous and saves time in practice. A complete lapping operationfor a pair of. blades can be carried out in not over thirty minutes. u

In the old method of makingtoothed blades for shears of vthistype where the cutters asthey form the teeth, revolve about an axis parallel to theblades 4,1the faces 1 and 8 of the teeth 'were not conical but were plain or flat, and they then had to be put through a preliminary shearing operation to form the narrow strips such as 2| along their leading or acute edges. The strips thus formed by shearing were made conical, with respect to an axis transverse to the wide flat sides of the blade, and at the right distance from one end, as; described. This shearing operation required only .a few minutes and the lapping not less than one hour. and a half. Also the inclination of the teeth had to be about 25 to the flat leading edges towards each other, and these edges 5 wide opposite sides of the blades 4; and even after lapping, the hand shears containing the toothed blades were hard to cut with and the teeth tended to rub, bind or. grind against the cloth when severing it. c V

" The lateral faces of the teeth were inclined to the wide flat sides of the blades because the teeth on one blade always have to clear and pass those on the other. If the lateral faces of the teeth between the pointed outer ends 9 and the inner ends or roots of the teeth were not inclined but perpendicular to the opposite, parallel fiat sides of theblades, the teeth with the blades close enough together to cut with their advance edges,

' would the n bind along the opposite or trailing edges; and the proper action of the shears could not'be obtained at all. The cuttin back or in clining of the lateral faces enables the teeth to clear along the trailing edges; but with the blades set to pass as near as possible, the advance'or leading edges of the teeth, which were sharper, would not always out clearly because thelead'in'g edges of the teeth would always come closer at some points than others, especially if said edges c oc-pars were straight along the sides of the teeth; 1. e.,-11f the faces 1 and 8 are plane or flat. 1

'The shearing of the teeth to produce a strip along the leading edges, thereof like that shown at 4 in Figures 5 and 6 improves the operation of the shears, if the strips are all elements "of conical surfaces having the common axi ab'ove mentioned. But if the remainder of 'th'elateral faces 1 and B are still flat; the shear bladesare': still liable to bind, are harder to work with, and will often cut'imperfectl'y and roughly. I

Withthe process described herein all' of the previous disadvantages are virtually eliminated, bec'ausethe teeth are cut on circular a'rcs about the c'enter of the shaft 2 as an axis and are formed so that. eachis :an element of a separate ical Surface as above stated. The inclination-o the teeth need not be more than and the strip-of surface-indicated at 2| does not have to be uniform in width; and yet the finished shears will work more easily and cut perfectly cleanly and smoothly in practice. The "shears. canalso b finished and assembled more rapidly.

The effect of processing, toothedblades in this manner is more clearly indicated in'Figures 7 8, 9 and 10. Each toothed blade is shownjwith' a rounded corner 25 which"may be taken asf'the outer end in the cutting or lapping stagesahd'in the finished unit. In Figure 7 the sidesfor, faces of the teeth "I, presented towards the axis'of the pivot 23, which corresponds to the position of the axis of revolution at the center of the shaft 2 when the milling operation is in progress, will be elements of conical surfaces but will be slightly concave between their edges in the opposite flat sides of the blades; and the other faces 8 of the teeth which are presented toward the outer ends of the finished shears, will be conical, but slightly convex from leading edge, to trailing edge. This appears more plainly in Figures 8 and 9. The shear blade marked A corresponds to'the one carried by the arm l8 and the lateral faces of whenever the .finishe'd'shears: are u'sedaforr divid ing cloth or t'rimming-thesame. f E

Figure 10 shows the" blades as disposed in the finished shears on'Figure' 7. The endswiththe curved corners 25 areatthe outer-ends of-the shears. One blade indicated at A'w-ill b'e-"secu'red to th'e upper member with the teeth away from the observer. wsee'n from underneath this blad'e will appear-as in F-i'gure-IO' with the acute or sharper leading edges of the teeth along the lower side-- The other bl'ade B will be secured. in its place ion'the "lower memberin Figure 7 with its teeth turned towards the observer "and its sharp leadingedges on top in' Figure 7'; -When the shears are made'to'cut, the lead-ing 'edges' of nee'ti'o'n with Figure's 2. and '7.

same non-radial positions as describedin eon- Eachconvex'lateral face 8 onth'e reenter either blade cooperates with the-concave face'of a tooth ion the Uther'blade." This is made plai'nby'Fig' ures' 8 i and 9-. Consider-for example the tooth at the right on bla'de 'Af Theface thereof at the right is convex across-the width thereoff-thatis' from one wide side of the blade to the other, and

' it will pass the concave face of the half tooth on the end of blade B, and so with all the other lateral faces on the two blades. In theory, each convex face and its associated concave face will be elements of one and the same conical surface, the convexity being outside and the concavity inside thereof. If perfect uniformity could be had,

the teeth which are slightly concave crosswise from one flat side of the blade to the other are indicated at V, while the faces which are convex are indicated by X. The same is true of the blade B, corresponding to the one held in the post l5. The blades A and B are both so cut in the manner shown by Figure 1 that the bottom edges of the teeth in Figures 8 and 9 are the leading or sharper edges; the blades being tilted on the disk I, as shown in Figure 3. In lapping, the rounded ends of the two blades are adjacent one another, and the teeth are so formed and situated in cutting, that the outer edge 9 of each tooth on one blade lies exactly at the intersection of two faces T and 8 of the teeth on the other, said intersectionbeing at the inner ends or roots of the last-named teeth. I

If the blade B in Figure 9 be visualized as it will appear if turned over horizontally about its rear edge in order to dispose the two blades A and B with their ends 25 still adjacent, so that I the teeth of blade B are presented to the teeth the teeth on one blade and the concave faces of the teeth on the matching blade rub together, as Figures 8 and 9 prove. The strip 2| will thus be easily formed and will give the results desired the convex faces and the matching concave faces would move past each other in close contact over their entire extent, and the leading edges would cut or shear the cloth along a zigzag or serrated edge with the utmost nicety, even if the faces I and 8 were not inclined, and not even lapping wouldbe necessary. The shearing effect would be efiicient to the last fraction of a degree, and the concave or arc-shapedstrip 2! also would not be required. However, perfect uniformity in dimensions and degree of curvature is not possible of attainment. These blades have to be produced in quantity by machine; and in the operation of machines there are alwaysvariations in result, due to differences in the hardness and other properties of the metal stock; the cut-' ters used;idiosyncrasies, so to speak, in the move- 1 ment of partsof the apparatus, such as might be brought about by one bearing or'connection having a microscopically larger or smaller fit, and other causes. The variations might amount to only a few thousandths of an inch; but they'will be sufficient to prevent the full realization of the ideal relationship between the convex and concave surfaces of the faces of the teeth on the two blades.

To enable corrections to be most easily and conveniently made. to compensate for errors of the kind just pointed out, the concave and convex faces land 8 are therefore inclined when first 7 cut by the members 5; and about ten degrees is chosen as most suitable for this purpose. This tilting or inclination is only a small departure from a perpendicular position with respect to the wide fiat opposite sides of the blades 4. Withthe concave and convex lateral faces I and 8 in r clined to this extent, and no more,,a1l the advantages enumerated above can be gained. But it is quite within the realm of possibility that this angle can be diminished; if mechanical apparatus capable of a greater-approach to perfect uniformity in operation and result can be designed and built.

During the lapping operation as carried out with the apparatus including the structure shown in Figure 4, the distance between the axis of the shaft [9 and the adjacent ends of the two blades is the same as the distance from the axis of the shaft 2 to the inner ends of the blades in the operation of cutting the teeth, and this distance is also exactly the same as the distance between the inner ends of the blades and the axis of the pivot 23 in the finished shears carrying theblades.

Having described my invention, what {believe to be new is:

1. A shear blade of uniform width and thickness with teeth to sever sheet material along a serrated line, said blade having parallel opposite flat sides, said teeth extending through the blade from one side to the other and having ends lying in the planes of said sides, and lateral faces which are elements of concentric" conicalsurfaces inclind at not more than ten degrees to said sides; the intersection of said'faces with one of said sides forming relatively acute edges, and a narrow strip of surface on each of said faces extending along the acute edge thereof, said strip hav- 8 ing a width of much less than half the-thickness of said blade. f" I 2. A shear blade of uniform width and thickness with teeth to sever sheet material along a serrated line, said blade having parallel opposite fiat sides, said teeth extending through the blade from one side to the other and having ends lying inthe planes of said sides, and lateral faces which are elements of concentric conical surfaces inclined at'not more than ten degrees to said sides, the intersection of said faces with one of said sides forming relatively acute edges, and a narrow strip of surface on each of said faces extending along the acute edge thereof, said strip having a width of much less than half the thickness'of said blade, said conical surfaces being alternately concave and convex over the lateral faces of the teeth.

' SAVA I. SHEER;

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS 

